The present invention relates to a device and method for packaging of a millimeter wave radio frequency integrated circuit (RFIC) and, more particularly, but not exclusively to such a packaging method that inexpensively and efficiently couples the RFIC to the waveguide.
Typically an RFIC at these frequencies would be mounted directly on the target printed circuit board (PCB) and bonded directly to it. Packages may be used, and typically these involve materials such as low temperature co-fired ceramic (LTCC) and silicon, and focus on printed antenna elements.
LTCC is a well-established multi-layer technology which has been in use for many years in the microelectronics packaging industry. Each of the layers are processed in parallel and only brought together in an accurately aligned stack immediately prior to firing. This contrasts with serially produced multi-layer structures such as thick film hybrid interconnects and components such as ceramic capacitors. LTCC technology is particularly used in RF and high-frequency applications. In RF and wireless applications, LTCC technology is also used to produce multilayer hybrid integrated circuits, which can include resistors, inductors, capacitors, and active components in the same package. LTCC hybrids have a smaller initial (“non recurring”) cost as compared with ICs, making them an attractive alternative to ASICs for small scale integration devices.
This technology presents advantages compared to other packaging technologies such as high temperature co-fired ceramic (HTCC). In LTCC, the ceramic is generally fired below 1000° C. due to a special composition of the material. This permits the co-firing to take place with highly conductive materials such as silver, copper and gold. LTCC also features the ability to embed passive elements, such as resistors, capacitors and inductors into the ceramic package, thus minimizing the size of the completed module.
An alternative is to use a ceramic based on a layer of aluminium and having a metal plug. Aluminium allows for molding and then etching of the components. The structure provides a platform, an upper layer and a cover.
In the known art, problems arise due to accuracy of the components, since with millimeter wave components, inaccuracies of a mere five microns can be critical. One solution is to use metal packaging. A metal box can be milled to very precise sizes. Also the metal has very good thermal properties so that heating due to radiation energy does not concentrate at particular location but is quickly dispersed.
The disadvantage with metal is price. Accurate machining makes the metal packaging very expensive. Nevertheless metal packaging is widely used in military applications, which are not price sensitive.